Apparatus for rectifying alternating currents.



No. 768,937. PATENTED AUG. 30, 1904. G. M. GREEN. I

APPARATUS FOR REGTIFYING ALfIERNATING OURRE'NTS.

APPLICATION FILED 00'1.26, 1900.

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lnvento r: Charles M. Green,

No. 768,937. PATENTED AUG. 30, 1904.

O. M. GREEN.

APPARATUS FOR REGTIFYING ALTBRNATING CURRENTS.

APPLICATION FILED OUT. 25, 1900.

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Witnesses:

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M W YM/MM UNITED STATES Patented August 30, 1904.

PATENT OEErc-E. 1

CHARLES M. GREEN, OF LYNN, MASSACHUSETTS, ASSIGNOR TO GENERAL ELEGTRIO COMPANY, A CORPORATION OF NEI/V YORK.

APPARATUS FOR RECTIFYING ALTERNATING CURRENTS.

SPECIFICATION forming part of Letters Patent No. 768,937, dated August 30, 1904. Application filed October 25, 1900. Serial No. 34,296. (No model.)

To (tZZ whom, it may concern:

Be it known that I, CHARLES M. GREEN, a citizen of the United States, residing at Lynn, county of Essex, State of Massachusetts, have invented certain new and useful Improvements in Apparatus for Rectifying Alternating Ourrents, of which the following is a specification.

One of the objects of my invention is to produce a rectified current which is practically free from pulsations and other irregularities.

such as are characteristic of the current produced byrectifying apparatus heretofore used. For obtaining this result I make use of a plurality of rectifying-commutators, each of'which is fed by an alternating current or currents, the current or currents supplied to one commutator being displaced in phase from the current or currents supplied to each of the other commutators. The direct-current brushes of these commutators are all connected in series, and the current therefrom is supplied to suitable consumption-circuits. Owing to the relative phase displacement of the respective currents supplied to the several commutators the pulsations due to one commutating device are compensated for by pulsations of an opposite character of the other commutating devices in such a manner as to produce a direct current of practically uniform character. To secure a proper source of supply for these various commutators, I make use of a novel form of phase-changing apparatus whereby an alternating current of a given number of phases may be changed into a system of currents having agreater number of phases, from which suitable selections are made of the currents to be supplied to each rectifying-commutator.

The particular features of novelty which characterize my invention are set forth more definitely in the appended claims, while for a better understanding of the details and mode of operation of my invention reference is to be had to the following description, taken in connection with the accompanying drawings, in which Figure 1 is a diagram of a system embodying my invention; Fig. 2, a modification thereof, and Fig. 3 a view of the transformer as constructed.

In Fig. 1 a source of three-phase current 1 is represented as supplying current to a systern of transformers (indicated generally at 2) by which the three phase current is transformed into six currents, each differing in phase from the other. These transformers may, if desired, be of the constant-current type-for example, such as are shown in the patent to Elihu Thomson, No. 516,8 I6, March 20, 1894. The currents thus transformed are grouped together and fed to a number of rectifyingecommutators, (indicated at 3, 4, and 5,) the grouping beingsuch that each commutator is fed by two currents differing in phase from each other by an angle of ninety degrees, the currents of one group, however, differing in phase from those of each of the other groups.

Upon examining the system of phase-changing transformers 2 it will be seen to consist of six primary windings, three of which, 6, 7, and 8, are connected in delta relation to each other and the remaining three, 9, 10, and 11, connected in Y -relation-that is, with a terminal of each to a common point 12. The three supply-mains 13, 14:, and 15 are connected to the terminals of the Y-connected windings and also to the three junctions of the delta-connected windings. The diagram of electromotive forces circulating in these pri mary windings is therefore represented by an equilateral trianglehaving its angles bisected by lines which meet at the center of the triangle. Each of the primary windings 6 to 11, inclusive, is provided with a secondary winding, these windings being indicated in the drawings at 16 to 21, inclusive. In these secondary windings electromotive forces are induced having the same phase relations to each other as exist between the corresponding currents in the primary windings.

The various rectifying-commutators are each of an ordinary construction used for rectifying electromotive forces in quarter-phase relation to each other, so that no particular description of the same is necessary. It is, however, desirable to point out the connections whereby each rectifier is supplied with quarter-phase electromotive forces an d whereby each of these sets of electromotive force is displaced in phase with respect to each of the other sets. The rectifier 3 derives its current from the secondaries 18 and 19. The el ctromotive force of the secondary 18 represents one side of a triangle of electromotive forces, while the electromotiveforce of the secondary 19 is represented by a line bisecting the angle opposite this side. As will be obvious from geometrical considerations, these two lines are at right angles to each other. In a similar manner the rectifier 4E is supplied with two electromotive forces in quarterphase relation to each other, these electromotive forces being derived from the secondaries 1 16 and 21. These electromotive forces are displaced ninety degrees from each other .in the manner already explained in connection with the electromotive forces in the secondaries 18 and 19. The two sets of electromotive forces supplied to the rectifiers 3 and 4 are not, however, in phase with each other, but are displaced by an angle of thirty degrees, this angle being represented by the angle between one of the sides of the triangle of electromotive forces and a line bisecting one of its adjacent angles, all of which will be readily understood by one skilled in the art. The rectifier 5 is supplied with electromotive forces derived, respectively, from the secondaries 17 and 20, one of which represents one side of the electromotive-force triangle and the other the bisector of the angle opposite this side. The set of electromotive forces supplied to the rectifier 5 are displaced in phase by an angle of thirty degrees from the set of electromotive forces supplied to the rectifier 4:. All of these rectifiers are supposed to be mounted upon the same shaft, or at least are driven synchronously with each other, and are displaced in angular position with respectto the commutating-brushes which bear thereon,

taken as a standard, by angles of thirty degrees. The brushes bearing upon these commutators are all connected 1n series to a consumption-circuit, which thereby has impressed of the closely-overlapping succession of the waves is practically uniform in value.

In order to reduce the maximum difference of potential operating in the consumption-cir- 'cuit, I may connect the several rectifyingcommutators 3, 1, and 5 together through the medium of circuits containing translating devices. These translating devices serve to consume a greater or less amount of the electromotive forces produced in the adjacent commutators, the result being that under these conditions the maximum difference of potential existing in the circuit is much less than if the rectifiers were connected directly in series without the interposition of some electromotive-force-consuming means.

Fig. 2 shows an arrangement of phasechanging transformers somewhat different from that shown in Fig. 1. In this arrangement I make use of but three transformers, each of which, however, is provided with a plurality of secondaries. One secondary of each set is connected directly to one of the rectifiers, while associated with that secondary is a combination of two secondaries corresponding, respectively, to the other two phases, the electromotive force of these two secondaries being combined in series with each other to produce a resultant displacement in phase ofninety degrees from the first secondary. 'For convenience the rectifiers are not shown in Fig. 2; but it will be understood that the set of leads 22 corresponds to one rectifier, the set 23 to another rectifier, and the set 2 1 to the remaining rectifier. The threephase mains supplying this arrangement of phase-changing transformers are shown at 25, 26, and 27. Three primary windings '28, 29, and 30 are connected in delta relation with each other and receive current through the three-phase mains 25, 26, and 27, which are connected, respectively, to the points of junction between the three primary windings 28 29 30. These primary windings are provided, respectively, with secondaries 31, 32, and 33, one of which supplies current directly to one of the rectifiers and the other secondaries to the other rectifiers, respectively. To obtain electromotive forces of such phase relation as to cooperate with the electromotive forces 31, 32, and 33 to produce therewith three sets of quarter-phase electromotive forces, I provide each of the primary windings of the phasechanging system with two additional secondaries, each having a suitable number of turns, these secondaries being indicated by the numerals 34 to 39, inclusive.

The secondaries 35 and 36 are connected in series With each other, thereby producing a resultant electromotive force which is displaced by equal angles from each of its components, or, in other words, is midway between them, and is therefore in quadrature with respect to the electromotive force of the secondary 33, corresponding to the remaining phase of the three sets of secondaries. The terminals leading from the secondary 33 and from the two secondaries 35 36 are therefore extended to and connect with the leads 22, which supply current to one of the rectifiers.

In a similar manner the leads 23 receive current from the secondary 31 of one of the phases and from the combined secondary windings 37 38of the other two phases. The leads 24 also receive current in like manner from the remaining secondaries 32, corresponding to one of the phases and the combined secondaries 34: and 39 of the other two phases.

While I have described the phase-changing devices above set forth as used in connection with rectifying-commutators, it is of course to be understood that they are not limited to use in this relation, but may be applied to any other purposes desired. I therefore wish my claims thereto construed broadly and without restrictive reference to the combinationsin which these phase-changing devices are shown.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent of the United States, is

1. The combination of a source of constantpotential alternating current of a given number of phases, and means for deriving ther from a constant current of a different number of phases.

2. The combination of a source of alternating current of a given number of phases, a transformer having relatively movable coils, connections between one set of coils and said source whereby constant-potential alternating current of a-given number of phases is supplied to the transformer, and connections between another set of said coils whereby current delivered by the transformer as constant alternating current is of a different number of phases from the current supplied to the transformer.

3. The combination of two sets of interconnected three-phase-transformer primary windings, one set connected in delta and the other in Y, and a single set of supply-mains for supplying energy to both sets.

a. The combination of two sets of three phase-transformer primary windings, one set connected in delta and the other in' Y, and secondary windings connected in inductive relation to said primary windings.

5. The combination of a plurality of rectifying commutators connected in series, and

phase-changing apparatus for supplying each of the commutators with alternating current.

- to another commutator, and a source of supply for delivering to said transforming device multiphase current of a number of phases different from that delivered by said device.

8. The combination of a source of multiphasecurrent,concatenated transformer-windings supplied with energy therefrom, and a plurality of series-connected rectifying-commutators receiving current derived from said transformer-windings.

9. The combination of two sets of threephase-transformer primaries one set connected in delta and the other in Y, a secondary winding for each primary, and a plurality of seriesconnected rectifying-commatators receiving current from'the secondary windings.

In witness whereof I have hereunto set my hand this 23d day of October, 1900;

CHARLES M. GREEN.

Witnesses:

G. E. LUFKIN, DUGALD McKILLoP. 

